<?php
/**
 *  @package FrameworkOnFramework
 *  @copyright Copyright (c)2010-2013 Nicholas K. Dionysopoulos
 *  @license GNU General Public License version 3, or later
 */

// Protect from unauthorized access
defined('_JEXEC') or die();

/**
 * A simple implementation of AES-128, AES-192 and AES-256 encryption using the
 * high performance mcrypt library.
 */
class FOFEncryptAES
{
	/** @var string The AES cipher to use (this is an mcrypt identifier, not the bit strength) */
	private $_cipherType = 0;
	
	/** @var string Cipher mode. Can be CBC or ECB. We recommend using CBC */
	private $_cipherMode = 0;
	
	/** @var string The cipher key (password) */
	private $_keyString = '';
	
	/**
	 * Initialise the AES encryption object
	 * 
	 * @param string $key The encryption key (password). It can be a raw key (32 bytes) or a passphrase.
	 * @param int $strength Bit strength (128, 192 or 256)
	 * @param string $mode Ecnryption mode. Can be ebc or cbc. We recommend using cbc.
	 */
	public function __construct($key, $strength = 256, $mode = 'cbc')
	{
		$this->_keyString = $key;
		
		switch($strength) {
			case 256:
			default:
				$this->_cipherType = MCRYPT_RIJNDAEL_256;
				break;
			
			case 192:
				$this->_cipherType = MCRYPT_RIJNDAEL_192;
				break;
			
			case 128:
				$this->_cipherType = MCRYPT_RIJNDAEL_128;
				break;
		}
		
		switch(strtoupper($mode)) {
			case 'ECB':
				$this->_cipherMode = MCRYPT_MODE_ECB;
				break;
			
			case 'CBC':
				$this->_cipherMode = MCRYPT_MODE_CBC;
				break;
		}
	}
	
	/**
	 * Encrypts a string using AES
	 * 
	 * @param string $stringToEncrypt The plaintext to encrypt
	 * @param bool $base64encoded Should I Base64-encode the result?
	 * @return string The cryptotext. Please note that the first 16 bytes of the raw string is the IV (initialisation vector) which is necessary for decoding the string.
	 */
	public function encryptString($stringToEncrypt, $base64encoded = true)
	{
		// Calculate the key to use for encryption
		$keySize = mcrypt_get_key_size($this->_cipherType, $this->_cipherMode);
		if(strlen($this->_keyString) != 32) {
			$key = hash('sha256', $this->_keyString, true);
		} else {
			$key = $this->_keyString;
		}
		
		// Set up the IV (Initialization Vector)
		$iv_size = mcrypt_get_iv_size($this->_cipherType, $this->_cipherMode);
		$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM);
		if(empty($iv)) {
			$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_RANDOM);
		}
		if(empty($iv)) {
			$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
		}
		
		// Encrypt the data
		$cipherText = mcrypt_encrypt($this->_cipherType, $key, $stringToEncrypt, $this->_cipherMode, $iv);
		
		// Prepend the IV to the ciphertext
		$cipherText = $iv . $cipherText;
		
		// Optionally pass the result through Base64 encoding
		if($base64encoded) {
			$cipherText = base64_encode($cipherText);
		}
		
		// Return the result
		return $cipherText;
	}
	
	/**
	 * Decrypts a ciphertext into a plaintext string using AES
	 * 
	 * @param string $stringToDecrypt The ciphertext to decrypt. The first 16 bytes of the raw string must contain the IV (initialisation vector).
	 * @param bool $base64encoded Should I Base64-decode the data before decryption?
	 * @return string The plain text string
	 */
	public function decryptString($stringToDecrypt, $base64encoded = true)
	{
		// Calculate the key to use for encryption
		$keySize = mcrypt_get_key_size($this->_cipherType, $this->_cipherMode);
		if(strlen($this->_keyString) != 32) {
			$key = hash('sha256', $this->_keyString, true);
		} else {
			$key = $this->_keyString;
		}
		
		if($base64encoded) {
			$stringToDecrypt = base64_decode($stringToDecrypt);
		}
		
		// Calculate the IV size
		$iv_size = mcrypt_get_iv_size($this->_cipherType, $this->_cipherMode);
		
		// Extract IV
		$iv = substr($stringToDecrypt, 0, $iv_size);
		$stringToDecrypt = substr($stringToDecrypt, $iv_size);
		
		// Decrypt the data
		$plainText = mcrypt_decrypt($this->_cipherType, $key, $stringToDecrypt, $this->_cipherMode, $iv);
		
		return $plainText;
	}
	
	/**
	 * Is AES encryption supported by this PHP installation?
	 * 
	 * @return boolean
	 */
	static public function isSupported()
	{
		if(!function_exists('mcrypt_get_key_size')) return false;
		if(!function_exists('mcrypt_get_iv_size')) return false;
		if(!function_exists('mcrypt_create_iv')) return false;
		if(!function_exists('mcrypt_encrypt')) return false;
		if(!function_exists('mcrypt_decrypt')) return false;
		if(!function_exists('mcrypt_list_algorithms')) return false;
		if(!function_exists('hash')) return false;
		if(!function_exists('hash_algos')) return false;
		if(!function_exists('base64_encode')) return false;
		if(!function_exists('base64_decode')) return false;
		
		$algorightms = mcrypt_list_algorithms();
		if(!in_array('rijndael-128', $algorightms)) return false;
		if(!in_array('rijndael-192', $algorightms)) return false;
		if(!in_array('rijndael-256', $algorightms)) return false;
		
		$algorightms = hash_algos();
		if(!in_array('sha256', $algorightms)) return false;
		
		return true;
	}
}
